Plumbing NC I flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Hierarchy of hazard control

The ranked order of risk reduction: eliminate the hazard, substitute it, apply engineering controls, then administrative controls, with personal protective equipment last because it protects only the wearer.

Confined space entry

Entry into a space with restricted access not meant for continuous occupancy. It requires a permit, atmospheric testing for oxygen and toxic or flammable gas, a standby person, and a rescue plan.

Lockout and tagout

Isolating energy sources before maintenance by closing valves, locking them, attaching a warning tag, then draining and verifying zero energy so the line cannot be re-energized unexpectedly.

Hydrogen sulfide hazard

A toxic gas found in sewers and pits. It is heavier than air, and at higher concentrations it deadens the sense of smell, so odour must never be used as a warning.

Manual handling limit

Keep loads close to the body and avoid twisting. Loads above roughly 25 kg generally require a two-person lift or a mechanical aid, depending on local regulation.

Pipe wrench jaw direction

Set the jaws so that pulling the handle drives the teeth into the pipe. Reversing the hook jaw suits the working direction, and cheater bars on the handle are prohibited.

Hacksaw blade selection

Choose teeth per inch by wall thickness: coarse blades for thick steel or copper, fine blades for thin-wall tube and plastic. At least three teeth should touch the work.

RCD and GFCI protection

A residual current or ground fault device that trips on leakage current to earth. It is required on portable electric tools used on site and should be tested before each use.

Soldering versus brazing

Soldering uses filler melting below 450 degrees Celsius; brazing uses filler melting above it, giving a stronger joint for higher temperatures and pressures.

Tool pre-use inspection

Checking guards, insulation, leads, plugs, and calibration before use. A damaged tool is tagged out of service and removed from the work area rather than used cautiously.

Drawing scale

The ratio of a drawn length to the real length, such as 1:50. Measure with the scale bar printed on the sheet rather than assuming a scale.

Riser diagram purpose

A schematic, not-to-scale drawing showing pipe sizes, fixture connections, vents, and floor levels in a vertical stack. It does not give horizontal distances.

Revision table

The block on a drawing listing revision letters, dates, and descriptions of changes. Always confirm the current revision before setting out or cutting material.

Request for information

A formal query raised when drawings and specifications conflict or details are missing. Work should not proceed on an assumption while the answer is pending.

Hidden line convention

A dashed line on a drawing showing construction that is concealed from the current view, such as pipe buried in a wall or passing under a floor slab.

Nominal pipe size

A size label that is neither the true outside nor inside diameter for all schedules. Outside diameter is fixed per nominal size, while inside diameter changes with wall thickness.

45-degree offset travel

For a 45-degree offset, travel equals the offset multiplied by 1.414. Subtract the fitting take-out of each 45-degree elbow to obtain the cut length.

Fitting take-out

The distance from the centre of a fitting to its face. Cut length equals the centre-to-centre measurement minus the take-out at each end of the pipe run.

Fall calculation

Fall equals run length multiplied by the gradient. A 12 m run at 1:60 falls 12 divided by 60, which is 0.2 m or 200 mm.

Waste allowance

Extra material added to a take-off to cover cutting losses and offcuts. About 5 percent suits straight runs, and about 10 percent suits complex fabrication.

3-4-5 squaring method

A layout check using a triangle with sides in the ratio 3:4:5, which has a right angle between the short sides. Used to square a setting-out line.

Deburring copper tube

Removing the internal and external burr left by a wheel cutter. An internal burr disturbs flow, causes noise, and can lead to erosion-corrosion at the joint.

Capillary solder joint

A joint where molten solder is drawn into the narrow gap between tube and fitting by capillary action. Clean surfaces, flux, even heat, and the right gap are essential.

Standard pipe thread taper

Tapered threads with a 1:16 taper, about 1.8 degrees. Hand-tight engagement is roughly three threads, and wrench-tight engagement is five to six threads.

Solvent welding sequence

Cut square, chamfer, clean with primer, apply cement to both surfaces, assemble with a quarter turn, and hold until set. Cure time increases with diameter and cold weather.

Pipe bending gain

The difference between the sum of the two leg lengths and the developed length of the bend. It must be allowed for when calculating the cut length.

Backflow prevention hierarchy

An air gap gives the highest protection, followed by a reduced-pressure zone assembly, then a double check valve. A single check valve is not adequate for high hazard.

Trap seal depth

The water depth in a fixture trap, typically 50 to 75 mm. It must be deep enough to resist pressure fluctuations and shallow enough to be cleared easily.

Vent stack function

A vertical pipe carrying air to the drainage system, protecting trap seals from siphonage and allowing sewer gases to discharge above the roof rather than into the building.

Drainage test before concealment

A water or air test of the drainage system carried out before pipes are covered. Results are recorded and defects corrected before the work is closed in.

Pressure-reducing valve setting

A valve that lowers supply pressure to a set downstream value, commonly around 300 to 500 kPa. A strainer is fitted upstream and expansion relief downstream on closed systems.

Trap primer purpose

A device that adds water to a floor drain trap to replace evaporation. Without it the seal is lost and sewer gas enters the building.

Temperature and pressure relief valve

A safety valve on a water heater that opens on excess temperature or pressure. It is piped to a safe discharge point and must never be plugged or capped.

Flush valve supply requirement

A flush valve needs a minimum supply pressure and flow stated by the manufacturer. Insufficient pressure causes weak flushing and repeated callbacks.

Grab bar anchorage

Grab bars must be fixed into structural framing or installed blocking, not into drywall alone, because they carry the full body weight of a person losing balance.